1. Field of the Invention
The invention concerns an airbag sensor system for actuating an airbag in a vehicle. The invention is suitable for use in both a side airbag system as well as in an alternative version adapted for use with a frontal airbag system.
2. Description of the Invention
Known airbag actuation systems employ acceleration switches or resistive films as actuators. The acceleration switches and also the resistive films respond to a collision with an external foreign body only after deformation of the automobile""s body has started. Because of the small crumple zone in the area of the door, and in the front area in certain vehicle types, a timely actuation of the airbags is of great importance for the safety of the occupants. It is also advantageous to take the relative speed of the colliding bodies into consideration as actuation criteria, since the actuation can thereby be suppressed in the event of an expected quasi-static deformation of the body. In the case of acceleration switches or resistance strips, a determination of the relative speed of the approaching colliding body is not possible.
The response time of the known airbag actuation systems is too long. The switches only respond after the deformation has been started. The switches and subsequent electronics of known systems require approximately 5 ms to generate a triggering impulse, within the total time of 20 ms that is available for deployment of the airbag in the case of a collision.
The invention is based on the task of generating a timely triggering time point for an effective airbag unfolding and therein to take into consideration the relative speed of the collision opponent as a triggering criteria.
The invention advantageously utilizes millimeter wave sensors to detect the relative speed of an object entering the vicinity of the motor vehicle. Besides this, the millimeter wave measuring results can be used to classify the colliding object according to size and shape and thus classify the object as to certain vehicle types or other objects such as for example poles, stones, etc. Using this classification system, the lack of knowledge of the mass of the collision object can be compensated for and therewith the actuation analysis can be improved with respect to the danger potential. An advantage of the use of millimeter wave sensors over the use of optical sensors is that no optical windows are required in the vehicle body and accordingly the sensors are not sensitive to dirt.